Research Interests

The contamination of chlorinated hydrocarbons and recalcitrant organic compounds in aquatic and subsurface environments has recently received highly attention. More and more trace amounts of toxic contaminants are released into the natural environments and accumulated in the subsurface environments. Traditional technologies focusing on the pollution control and end-of-pipe treatment are now hard to meet the criteria of the complexity of the natural environments. The understanding of the molecular-level fate and transport of toxic chemicals in the environmental is urgent to better understand the reaction kinetics and mechanisms of pollutants in the environments. In addition, the development of innovative environmental technologies to effectively decompose/control priority pollutants is needed. Therefore, the research interests of Dr. Doong primarily lie in three major areas: (1) Remediation of Pollutants in the Subsurface Environments, (2) Environmental Analysis and Monitoring of Toxic Chemicals, and (3) Fabrication of Environmentally Benign Nano-materials for Treatment and Remediation.

•  Remediation of Pollutants in the Subsurface Environments

The research interest in this area mainly focuses on development of (1) remedial technologies to effectively degrade trace organic compounds in water and porous media, and (2) molecular-level technique to understand the possible reaction kinetics and mechanisms of pollutant at solid-liquid interface. The use of zerovalent metals (Fe(0), Si(0), Pd/Fe, and Cu/Fe) and surface-bound iron species as reductants to reduce organic compounds is of great interest in Dr. Doong's group. The dechlorination kinetics and mechanisms of biotic and abiotic degradation of chlorinated hydrocarbons under iron-reducing conditions are investigated using GC/MS, XRD, and XPS to understand the fate and transport of trace toxic chemicals in the subsurface environments. Moreover, addition of low concentration of metal ions (e.g. Cu(II), Ni(II)) to enhance the degradation efficiency and the rate of chlorinated hydrocarbons by surface-bound iron species and zerovalent metals will also be emphasized to understand the synergistic effect of organic pollutants and metal ions on degradation and immobilization under iron-reducing conditions.

In this research area, we published the first paper of using zerovalent silicon (Si 0 ) to significantly enhance the dechlorination rate of chlorinated hydrocarbons in groundwater remediation. The combination of zerovalent silicon with zerovalent iron (Fe 0 ) not only accelerates the dechlorination rate but also change the distribution of end products to the lesser chlorinated compounds. We also proved that cysteine can serve as electron carrier to transfer electrons from Geobacter sulfurreducens to ferric oxides. The dissolution rate of Fe(OH) 3 in the presence of cysteine is 8 – 11 times higher than that without the addition of cysteine. Moreover, addition of low concentration of Cu(II) greatly enhance the abiotic dechlorination efficiency and the rate of chlorinated hydrocarbon by Fe(II) associated with goethite or green rust. Cu(II) can be reduced to Cu(I) by Fe(II) and Cu(I) acts as catalyst to enhance the dechlorination rate of chlorinated compounds under iron-reducing environment. However, the interaction between abiotic and biotic transformation of priority pollutants and the electron flows from iron species to target compounds remains unclear. Further research will focus on (1) the interaction of biotic and abiotic transformation of organic compounds under iron-reducing environments, and (2) the reduction of priority organic pollutants and heavy metals by zerovalent metals in soil and groundwater.

•  Environmental Analysis and Monitoring

The development of environmental analytical techniques for the rapid determination of persistent organic pollutants and toxic chemicals in the environmental media is of great importance to understand the distribution and fate of persistent organic pollutants (POPs) and toxic chemicals in the environments. In this area, we mainly focus on the fabrication of array-based biosensors and nanosensing systems for the detection of environmental pollutants.

The rapid and precise sensing system capable of detecting pollutants or hot spots at molecular level could greatly enhance the ability of understanding transport and fate of organic pollutants in the environments. Different formats of sensing systems including microarray, biosensors, and array-based sensors have been successfully developed in Dr. Doong's lab for detecting and monitoring the toxic chemicals in aqueous solutions. Sol-gel based array biosensors for multi-analyte and multi-sample analyses are also developed in this area. We have successfully fabricated a 144-spot sol-gel–derived array biosensor for the determination of various compounds including urea, acetylcholine, glucose, organphosphorus pesticides, and heavy metals. These developed array-based sensing systems will be further used for (1) real time analysis of multi-analytes, (2) continuous monitoring the concentration change of contaminants, (3) evaluating the remediation efficiency, (4) groundwater resource management, and (5) risk assessment.

•  Fabrication of Environmental Benign Nanomaterials for sensing and Treatment.

Over the past decades, much effort has been made in understanding environmental phenomena at the macro-scale magnitude and in technology development for the control and mitigation of environmental pollutants. Nanotechnology is now becoming an innovative technology to clean up the past contaminants and perverse the future environments. It offers a whole new perspective and research opportunity on exploring the fate and transport of environmental pollutants at micro-scale levels, and providing new materials for effectively decomposing recalcitrant pollutants. In this area, Dr. Doong's interests lie in the fabrication of environmentally benign metal nanoparticles and doped nanomaterials for the application to the detection of biomolecules and analytes and to the advanced oxidation processes (AOPs) in aqueous solution. We have successfully fabricated the ordered porous TiO 2 thin film with high specific surface area for photocatalysts. The microstructure and chemical composition of doped TiO 2 and ZrO 2 nanomaterials have been investigated. The further research will be focus on (1)intra-particle electron transfer (IPET) system using nanocomposite TiO 2 -ZrO 2 and other semiconductors (TiO 2 -SiC) to enhance the degradation efficiency of chlorinated compounds, (2) fabricating porous nanomaterials to effectively decomposed environmental pollutants in aqueous and subsurface environments, (3) developing the core-shell nanocomposite materials for nanosensing biomolecules and analytes, and (3) fabricating of supramolecules such as dendrimers and molecularly imprinted polymers (MIP) as nanosensing materials and stationary phases for analysis
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